An imidazole compound is widely used as a raw material for a medicine and a pesticide, a metal surface treatment agent, or a curing agent or a curing accelerator for epoxy resin.
When an imidazole compound is used as a curing agent or a curing accelerator for epoxy resin, there is an advantage that the epoxy resin may be cured in a short time at a low temperature, and that the mechanical properties, electrical properties, and the like of the cured product are satisfactory. On the other hand, there has been a problem that the curing reaction starts at room temperature, reducing storage stability. Therefore, there has been an attempt to give latency to an imidazole compound by forming a clathrate compound of the imidazole compound, and the following methods are known as a method for producing a clathrate compound comprising an imidazole compound.
Patent Document 1 describes that, as a method for producing a clathrate compound comprising 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane (hereinafter also referred to as TEP) and 2-phenyl-4-methyl-5-hydroxymethylimidazole (hereinafter also referred to as 2P4MHZ), crystals of the clathrate compound are obtained by suspending TEP and 2P4MHZ in ethyl acetate, heating the suspension under reflux for 3 hours, and then cooling the suspension to room temperature.
Further, a clathrate compound comprising at least an isophthalic acid compound and an imidazole compound is known, and Patent Document 2 describes that, as a method for producing the same, crystals of the clathrate compound are obtained by adding a methanol solution of 2-ethyl-4-methylimidazole (hereinafter also referred to as 2E4MZ) to a methanol solution of 5-nitroisophthalic acid (hereinafter also referred to as NIPA) with stirring under heating under reflux and then cooling the mixture overnight at room temperature after heating.
Patent Document 3 describes that, in an epoxy resin composition for sealing semiconductors which comprises an epoxy resin (A) and a clathrate complex (B) comprising 5-hydroxyisophthalic acid and 2-ethyl-4-methylimidazole, crystals of the clathrate complex are obtained by dropwise adding an ethyl acetate solution of 2E4MZ with heating to a mixture of 5-hydroxyisophthalic acid (hereinafter also referred to as HIPA) and ethyl acetate and then heating the resulting mixture under reflux for 2 hours.